p  n.  y; 


or 


. 


Issued  Junuarj  27,  1910, 


U.  S.  DEPARTMENT  OF  AGRICULTURE 

BUR]  Ai     0]    PLAN  I    INDUSTRY     Circular  No.  S 
B.    I  .  GALLOW  W,  • 


rP 


TILE  S.MITS  OF  SORQHUM. 


EDWARD  M.  FREEMAN,  Pathologist, 


HARRY  J.  C.  UMBERGER,  Scientif*    Assistant, 
Office  of  Grain  [Investigations. 


21336     in 


WASHINGTON    :  GOVERNMENT  PRINTING  Orrif 


[Cir.  8.] 
2 


BlREAl    OF  PLANT  INDUSTRY. 


Bureau,  Beverly  T.  Galloway. 
:  (  Mefof Bureau,  Albert  F.  Woods. 
Editor,  J.  E.  Rockwell. 
'  Urk,  James  E.  .!• 


CONTENTS. 


[ntroduetion 

Kin  hum  smuts 

Grain  I    - 1 1 1 1 1 1         il 

Treatn  rain  smut. .  <; 

Formalin  treatmenl  <; 

Hot-water  treatmenl 7 

Copper  sulphate  treatmenl  7 

Head  smul > 

ns g 

Cir.8.]  3 


Digitized  by  the  Internet  Archive 
in  2013 


http://archive.org/details/smutsoOOunit 


B.  II       :   i 


THE  SMUTS  OF  SORGHUM: 


INTRODUCTION. 

The  smuts  are  among  the  most  destructive  enemies  of  sorghums. 
It  1 1 1 ; i \  be  thai  the  actual  loss  from  smut  in  these  highl}  importanl 
crops  is  not  at  presenl  as  serious  as  that  sustained  by  oats  and  wlieat, 
but  it  is  nevertheless  quite  considerable  and  is  certainly  serious  in 
some  localities.  The  chief  danger  from  these  smuts  is  the  probabil- 
ity of  their  rapid  spread  if  proper  precautions  are  not  taken  to  hold 
them  in  check.  The  area  where  sorghum  crops  are  grown  is  being 
rapidly  extended,  and  with  this  extension  the  smuts  may  easily  be 
distributed  over  nevs  areas.  I>\  using  simple  precautions  al  the  pres- 
enl time,  farmers  may  avoid  much  disappointment  and  loss  in  the 
future.  The  losses  caused  by  smuts  of  oats,  barley,  and  wheat 
throughout  the  United  States  oughl  to  prove  a  sufficient  warning 
to  all  farmers  and  communities  which  are  now  either  growing  or  in- 
troducing sorghum  crops,  because  the  smuts  of  sorghums  may  yet 
i -a u-e  as  much  damage  as  t  hose  of  the  other  cereals  mentioned. 

The  objects  of  this  circular  are  (1)  to  call  attention  to  these  danger- 
ous pests,  (2)  to  w  a rn  farmers  of  the  danger  of  introducing  t  hem  into 
new  localities,  and  (3)  to  suggest  simple  methods  of  getting  rid  of 
them  if  they    ,ne  already  present. 

KINDS  OF  SORGHUM  SMUTS. 

There  are  in  this  country  two  well-known  smuts  of  sorghums:  The 
grain,  or  kernel,  smut  (SpTiacelotheca  sorghi  (Link)  Clinton)  and  the 
head  smut    (Sphacelotheca  reiliana   (Kuhn)  Clinton). 

The  grain,  or  kernel,  smut  is  easily  distinguished  by  the  fact  that 
"id\  the  individual  kernel-,  or  grains,  are  affected,  while  the  head 
retains  its  usual  form  and  nearly  its  usual  appearance.  Most,  if  not 
all,  of  the  kernels  in  a  smutted  head  are  usually  destroyed.  Each 
kernel  is  changed  into  a  more  or  less  conical,  grayish  to  reddish  mass 
containing  the  dark-colored  smut  dust,  or  spore-. 

The  head  smut  is  very  different  in  appearance.  The  whole  head. 
just  as  it  emerges  from  the  upper  leaf,  is  converted  into  a  single  huge 
smut   mass,  covered  by  a  whitish  or  grayish  membrane,  which  soon 

"  rn  recenl  years  there  has  been  a  \  cry  rapid  settlement  of  the  semiarid  lands.  The 
Borghums  are  among  the  most  suitable  crops  for  cultivation  on  such  lands,  and  many 
inquiries  are  received  by  iliis  Bureau  for  information  in  regard  to  the  sorghum  smuts. 
The  first  edition  of  Circular  No.  8,  on  these  smuts,  is  exhausted.  This  revised  edition 
ictical  knowledge  of  these  disi  isi  and  alt  >  such  improvements  in  the  li"t- 
water  treatment  for  the  grain  Bmul  as  are  a<l\  isable  in  the  lighl  of  further  investiga- 
tions.    B.  T.  ( I  \l  I  OW  \  i , 


6  THE    SMUTS    OF    SORGHUM. 

bursts  .-Hid  sots  the  spores  free.  In  this  smut,  therefore,  all  trace  of 
the  individual  grains,  or  kernels,  is  lost.  The  smut  mass  resembles 
somewhat    in   appearance  a  smut   mass  on  corn. 

It  is  not  yet  known  how  many  of  the  various  groups  and  varieties 
of  sorghum  each  smut  infects.  The  grain  smut  occurs  on  all  of  the 
principal  groups,  while  the  head  smut  has  been  observed  on  sorgos 
(sweet  sorghums),  kalirs.  and  shallu.  Neither  smut  has  been  ob- 
served on  milo  up  to  the  present  time,  and  attempts  to  inoculate  milo 
with  the  kernel  smut  of  kafirs  ami  sorgos  have  proved  unsuccessful. 

GRAIN.  OR  KERNEL,  SMUT. 

Of  the  two  smuts  of  sorghum,  the  kernel  smut  is  at  present  the  more 
widely  distributed.  It  is  found  almost  universally  where  sorghum 
crops  are  grown.  The  losses  sustained  are  in  many  districts  very 
severe.  They  are  increasing  and  will  continue  to  increase  unless  pre- 
ventive measures  are  adopted. 

The  life  history  of  this  grain  smut  is  now  well  known.  It  is  similar 
to  that  of  stinking  smut,  or  bunt,  of  wheat,  viz,  the  spores,  or  smut 
dust,  get  on  the  kernels  in  thrashing  or  in  handling,  and  when  the  seed 
is  planted  they  grow  at  the  same  time  that  the  seed  sprouts.  The 
smut  plant  penetrates  the  stalk  of  the  young  seedling  plant  and  grows 
inside  of  the  latter  until  the  heads  are  formed,  when  the  fungus 
forms  its  spores  inside  of  the  grains,  replacing  the  latter. 

As  in  the  bunt  of  wheat,  careful  seed  treatment  will  kill  the  smut 
spores,  because  the  latter  cling  to  the  outside  of  the  seeds,  and  after 
such  treatment  the  crop  will  be  free  from  smut. 

It  is  therefore  very  important  that  any  farmer  who  is  not  sure  that 
his  seed  is  free  from  smut  should  treat  his  seed  in  one  of  the  ways 
suggested  in  this  circular.  When  his  seed  is  once  clean  he  can  keep 
his  farm  free  from  smut  by  raising  his  own  seed,  provided  he  does  not 
allow  it  to  become  smutted  again  in  a  smutty  thrashing  machine  or 
in  the  subsequent  handling  of  the  grain. 

TREATMENT  OF  GRAIN  SMUT. 

Seed  that  is  smutty  may  lie  t  reated  in  the  following  ways: 

FORMALIN    TREATMENT. 

Mix  1  pound  of  full-strength  formalin  with  30  gallons  of  water. 
Put  the  seed  in  sacks  and  immerse  the  sacks  in  this  solution  for  one 
hour,  stirring  ii  occasionally.  Then  take  the  sacks  out  and  set  them 
to  drain.  Spread  the  seed  out  on  a  clean  floor  or  canvas.  He  sure 
that  all  of  the  sacks,  the  bain  floor,  and  the  canvas  used  in  handling 
the  grain  after  t  real  ment  are  cleaned  either  with  boiling  water  or  with 
a  strong  formalin  solution.  The  seed  will  be  infected  again  if  any 
untreated   smut    spores  touch    it.      When   the  seed    is  sufficiently  dry 

after  t  real  ment   it    may  be  sown.      • 
[Cir.  8.] 


THE   SM  I'  is    i  GHUM. 


The  same  solution  ma}  also  be  used  us  a  spnn  .  in  which  case  the 
seed  to  be  i  reated  should  be  spread  oul  on  a  clean  floor  or  i-mw  as  and 
sprinkled  with  the  solution.  It  must  be  shoveled  over  frequently 
until  all  of  the  seeds  arc  wet.  U  ma\  then  be  shoveled  into  a  pile 
and  left  over  night,  covered  with  a  clean  canvas  or  sacking  to  keep 
in  the  fumes,  and  then  spread  oul  to  drj  in  the  morning.  Seed 
treated  in  this  way  will  be  free  from  smut.  The  immersion  method 
is  more  thorough,  but  is  not  as  convenient  as  the  sprinkling  method. 

IIOT-W  A  111:     rREATM  INI. 

Hot  water  is  a  most  cheap  and  efficient  means  of  treating  sorghum 
seed.  The  I  real  n km 1 1  is  more  easily  applied  to  sorghum  than  to  wheat 
and  barlej  .  because  sorghum  seeds  (at  least  those  of  kafirs  and  sorgos, 
or  sweet  sorghums)  will  stand  much  higher  temperatures  than  wheal 
and  barley  seeds.  The  smaller  quantity  of  seed  used  to  the  acre  in  the 
sorghum  crops  is  an  additional  advantage,  making  it  possible  to  treat 
easily  all  the  seed  required  for  a  large  area.  In  the  hot-water  treat- 
ments of  sorgo  and  kalir  a  I'airU  wide  range  of  temperature  is  per- 
missible, and  the  operation  is  therefore  easily  performed  on  the  farm. 

In  brief,  the  process  is  as  follows:  Heat  two  large  vats  or  tubs  of 
water  to  aboul  135  and  140  F.,  respectively.  Place  the  seed  to  be 
treated  in  a  clean  sack  or  wire  basket  and  plunge  it  into  the  tub  of 
water  heated  to  135  P.  for  a  moment.  Then  transfer  the  sack  to  the 
second  tub  or  vat  for  ten  to  twelve  minutes.  Keep  the  temperature 
of  the  water  in  the  second  tub  between  134  and  I  III  I''.  It  should 
QOl    be  allowed   to  go  above    1  12     or  below    134      V.      The  seed  .should 

be  frequently  stirred  in  order  to  keep  the  temperature  uniform 
throughout.  Small  sacks  should  be  used,  since  in  large  sacks  it  is 
impossible  to  keep  the  temperature  constant.  After  this  treatment 
eed  is  spread  out  to  dry  on  a  clean  floor  or  canvas.  When  suffi- 
cient l\  dry  it   may  be  sow  n. 

A.S  in  the  formalin  treatment,  ever}  precaution  must  be  taken  to 
prevenl  infection  of  the  seed  after  treatment.  Although  this  treat- 
ment is  not  as  convenient  as  the  formalin  method,  it  is  just  as  effi- 
cient, is  cheaper,  and.  on  account  of  the  wide  range  of  temperal ure,  is 
easily  applied.  It  is  superior  to  the  formalin  method  in  that  the 
farmer  docs  not  have  to  rely  on  a  druggist  for  the  strength  of  a  forma 
lin  solution.  If  the  formalin  is  not  of  full  standard  strength  (i.  e.,  a 
10  per  cenl  solution),  the  formalin  treatment  ma\  not  be  successful. 
In  the  hot-water  treatment  all  of  the  implements  and  materials  are 
directly  under  the  control  of  the  fanner. 


COPPER    st  I. I'll  VI  I      I  i;i    \  I  \i  I  \  i 


Solution-  of  copper  sulphate  (bluestone)  also  give  satisfactory 
results,  but  are  certainly  no  better  than,  and  probably  not  even  as 
good  as,  the  two  methods  described  above. 

[Clr.  8.] 


8 


THE    SMUTS    OF    SORGHUM.  ?==ht 

HEAD   SMUT.  i^=<3) 

=  CM 


At  present  the  head  smut  does  not  occur  in  abundance  beyond  a   o 
very  restricted  area  in  the  Panhandle  of  Texas.     Its  life  history  is  £_. 
not  yet  understood,  but  enough  is  known  to  show  that  the  treatments  *rao 
recommended  for  the  grain  smut  have  absolutely  no  effect  upon  the   1=^ 
head  smut.     This  indicates  that  this  disease  may  be  more  difficult    ^|gj 
to  control  than  the  grain  smut  when  once  it  succeeds  in  getting  a  fair      = 

start. 

The  only  recommendation  that  can  be  made  at  the  present  time  is 
to  keep  the  smut  away  from  the  farm  and  the  community.  In  order 
to  do  this  the  farmer  must  be  sure  that  his  seed  did  not  come  from  a 
crop  that  contained  head  smut,  If  it  is  allowed  to  spread  unchecked, 
it  bids  fair  to  become  troublesome  in  the  future.  In  case  it  is  already 
present  on  the  farm  the  infected  plants  should  be  cut  out  completely 
and  burned  before  the  smut  spores  have  a  chance  to  scatter. 

RECOMMENDATIONS. 

The  precautions  necessary  and  the  proper  treatments  for  the  smuts 
of  sorghum  crops  may  be  summarized  as  follows: 

(l)&If  possible,  get  seed  free  from  smut— from  fields  that  are 
known  to  have  had  no  smut  during  the  preceding  year.  Also  be  sure 
that  such  seed  has  not  become  smutted  in  harvesting  and  handling 

(2)  Keep  your  farm  free  from  smut  by  using  your  own  seed  and 
employing  only  machinery  that  will  not  contaminate  your  crop. 

These  first  two  precautions  will  insure  you  against  both  kinds  ot 

smut,  .„ 

(3)  Treat  your  seed  with  either  formalin  or  hot  water  it  you  are 
not  sure  that  it  is  free  from  smut.  This  will  not  necessarily  insure 
the  farm  against  head  smut. 

(4)  Maintain  a  quarantine  against  any  locality  or  hum  wtiere 
smut  is  known  to  exist,  as  well  as  against  any  seed  grower  who  allows 
smut  in  his  fields.     This  course  will  largely  prevent  the  spread  ot 

both  kinds  of  smut. 

(5)  Maintain  a  quarantine  against  any  handlers  of  machinery  who 
allow  their  machinery  to  become  or  remain  contaminated  with  smut 
spores.  This  would  be  effective  against  the  gram  smut.  It  would 
probably  have  no  effect  on  the  head  smut,  however. 

(6)  Milo  has  not  yet  been  reported  as  subject  to  either  smut,  and 
hence  may  probably  be  safely  grown  without  treatment. 

Approved  : 

James  Wilson, 

Secretary  of  Agriculture. 

Washington,  D.  C,  April  22,  1908. 

[Cir.8.]  \~ 


